time — time + delays

import time

DOS has a BIOS tick counter (INT 1Ah AH=0) at ~18.2 Hz (one tick every ~55 ms). All time functions are built on this counter or on the CMOS RTC.

Wall-clock time

time.time() — Unix epoch seconds (32-bit)

Returns seconds since the Unix epoch (1970-01-01 UTC). On this port the resolution is ~1 second (CMOS RTC tick).

>>> time.time()
1747630800            # 2026-05-19 ...

⚠️ This is a 32-bit value (mp_timestamp_t = mp_uint_t). Good through year 2106 (2038 if signed). If you need nanosecond resolution, use time.time_ns() — but heads-up that on a 386 class machine the granularity is still the BIOS tick, so time_ns() returns multiples of ~55 million.

time.time_ns() — same, nanoseconds

>>> time.time_ns()
1747630800123456000

time.localtime(secs=None) / time.gmtime(secs=None)

Convert epoch seconds to a (year, mon, mday, hour, min, sec, weekday, yearday) tuple. With no arg, uses time.time().

>>> time.localtime()
(2026, 5, 19, 14, 30, 0, 0, 139)

⚠️ No timezone support — localtime() and gmtime() return the same thing (whatever the DOS clock reads).

time.mktime(tuple)

Inverse: convert a struct-time-tuple back to epoch seconds.

>>> time.mktime((2026, 5, 19, 14, 30, 0, 0, 139))
1747662600

Ticks (monotonic)

time.ticks_ms() / time.ticks_us()

Monotonic millisecond / microsecond counter. Wraps modulo 2**30 (so a ticks_diff is needed to compare).

>>> t0 = time.ticks_ms()
>>> do_stuff()
>>> elapsed = time.ticks_diff(time.ticks_ms(), t0)
>>> print('took', elapsed, 'ms')

time.ticks_diff(a, b) — a - b with wraparound handling

Always use this instead of subtracting ticks directly:

delta = time.ticks_diff(time.ticks_ms(), t_start)
if delta > 5000:
    print('5 seconds elapsed')

time.ticks_add(t, delta)

Add a delta to a ticks value, with wraparound handling.

Sleep

time.sleep(seconds) — float seconds

time.sleep(0.1)        # 100 ms
time.sleep(1)

time.sleep_ms(ms) / time.sleep_us(us)

time.sleep_ms(50)
time.sleep_us(500)     # 500 µs (best effort — BIOS tick is 55 ms)

Implemented as busy-wait on the BIOS tick counter. CPU is consumed during the sleep — DOS has nothing to switch to.

Performance counter

time.perf_counter() — seconds (float), monotonic

Same source as ticks_ms, but scaled. Useful for benchmarks:

t0 = time.perf_counter()
do_thing()
print(time.perf_counter() - t0, 'seconds')

Example: timeout loop

import time

t_end = time.ticks_add(time.ticks_ms(), 5000)   # 5-second deadline
while time.ticks_diff(t_end, time.ticks_ms()) > 0:
    if check_something():
        break
    time.sleep_ms(10)
else:
    print('timed out')

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Credit: signatures from MicroPython time docs (MIT). DOS-specific notes are this port’s.